Subsurface drainage system

ABSTRACT

The present invention is directed to a subsurface drainage system for a playing surface. The subsurface drainage system includes a subgrade, an intermediate layer disposed over the subgrade, a layer of semi-permeable filter fabric disposed over the intermediate layer, an upper permeable layer disposed over the layer of filter fabric and on which the playing surface is disposed, and a hydronic piping network disposed in the upper layer near the layer of filter fabric. The layer of filter fabric has a permeability less than the permeability of the intermediate layer and such that the layer of filter fabric functions as a perching layer to support a perched water table above the filter fabric. The hydronic piping network is positioned within the perched water table such that the water of the perched water table functions as a heat exchanger to facilitate heating and cooling of the upper layer upon the hydronic piping network being heated or cooled.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No.60/600,095, filed Aug. 9, 2004, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a subsurface drainage system forfacilitating water drainage from a land surface, and more particularlybut not by way of limitation, to improved subsurface drainage system foran athletic field, such as a putting green or football field, whichsubsurface drainage system is capable of retaining adequate water tofacilitate turf growth and temperature regulation while promoting rapidinfiltration of water through the subsoil structure.

2. Brief Description of Related Art

Conventionally, drainage for athletic fields, such as football fieldsand putting greens, has been constructed with the use of a network ofdrain pipe buried under the playing surface. The drain pipe is providedwith a multiplicity of perforations in the circumferential wall thereof.Rainwater or irrigation water penetrating into the playing field isintroduced into the drainage pipe through the perforations in thecircumferential wall thereof, collected to a trunk pipe, and drained.

Today, most playing fields are constructed to have an intermediate layercomprising gravel and a root zone layer comprised primarily of sand topromote drainage and thus prevent root rot of the turf grass. As such,even a small amount of water rapidly penetrates the root zone layer andpasses into the drainage system. Agricultural chemicals or fertilizersthat are used to maintain or control the grass also flow out togetherwith the water.

During warm weather months, watering of natural grass playing fields isrequired for growing and maintaining the grass. With the conventionalconcentrated drainage system, however, a putting green having a root mixlayer comprised primarily of sand would require watering at least abouttwice per day in summer, even if a water-retaining material such asperlite or pumice is incorporated as an improving material in the rootmix. Such watering requires time and labor.

Additionally, temperature variation can cause problems in maintaininghealthy grass for certain temperature sensitive grasses. To this end,piping networks have previously been installed in the subsurface in anattempt to regulate the temperature of the root zone layer. The same istrue with respect to artificial turf surfaces in attempt to maintain asafe playing surface, one which is not too hot or too cold. The problemencountered with such piping networks is that it is difficult touniformly heat or cool the root zone layer without employing a densenetwork of pipes. Obviously, increasing the amount of pipe usedincreases the cost of the system. It would be preferred to obtain auniform distribution while using a minimum amount of pipe.

In view of the above-mentioned concerns, a need exits for a subsurfacedrainage system that is capable of retaining adequate water whilepromoting rapid infiltration of water through the subsoil structure andwhich is adapted to uniform temperature regulation. It is to such asubsurface drainage system that the present invention is directed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic sectional view illustrating a subsurface drainagesystem for natural turf constructed in accordance with the presentinvention.

FIG. 2 is a schematic sectional view illustrating another embodiment ofa subsurface drainage system for natural turf constructed in accordancewith the present invention.

FIG. 2A is a top cutaway view of FIG. 2 illustrating a hydronic pipingnetwork for natural turf constructed in accordance with the presentinvention.

FIG. 3 is a schematic sectional view illustrating another embodiment ofa subsurface drainage system for natural turf constructed in accordancewith the present invention.

FIG. 4 is a schematic sectional view of a subsurface drainage system forartificial turf constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, showntherein is a subsurface drainage system 10 constructed in accordancewith the present invention. The subsurface drainage system 10 is similarto that recommended by the United States Golf Association for theconstruction of putting greens with the exception that the subsurfacedrainage system 10 includes a semi-permeable filter fabric layer at thebottom of the root zone layer. The 2004 revisions of the USGARecommendations for a Method of Putting Green Construction is herebyexpressly incorporated herein by reference. More particularly, thesubsurface drainage system 10 of the present invention includes asubgrade or base 12, an intermediate layer 14, a semi-permeable filterfabric layer 16, an upper or root zone layer 18, and a turf layer 20.Optionally, an impermeable liner 22 is disposed between the base layer12 and the intermediate layer 14. In instances where it is desirable toallow some permanent deep infiltration of surface drainage, theimpermeable liner 22 may be replaced with a semi-permeable geotextilefabric.

The base layer 12 is graded according to methods and designs known inthe art to define one or more surfaces sloping down to points or linesof fluid collection (not shown). The base layer 12 should be thoroughlycompacted to prevent settling.

The intermediate layer 14 provides a drainage blanket and is thereforeformed of materials, such as crushed stone, pea gravel, rubberparticles, or combinations thereof. As used herein, “intermediate layer”means a gravel layer or a gravel layer and an intermediate layer asthose terms are used by the USGA in its recommendations for a method forconstructing a putting green.

The root zone layer 18 is generally comprised of a homogenous mixture ofsand, organic matter, and inorganic matter.

The filter fabric layer 16 is interposed between the intermediate layer14 and the root zone layer 18. When a filter fabric layer 16 is notinterposed between the root zone layer 18 and the intermediate layer 14,the sand of the root zone layer 18 can become commingled with theintermediate layer 14 and thereby effect the permeability of theintermediate layer 14 and the water retention capacity of the root zonelayer 18. The filter fabric layer 16 will function to prevent particlesfrom the root zone layer 18 from migrating into the intermediate layer14, thereby maintaining the permeability of the intermediate layer 14.

The permeability of the filter fabric layer 16 is less than thepermeability of the intermediate layer 14. As such, the filter fabriclayer 16 will function to distribute and support a uniform layer ofwater above the filter fabric 16 in the form of a perched water table24. Because the permeability of the filter fabric 16 is substantiallyuniform, the perched water table 24 will have a substantially uniformheight which will promote uniform turf growth. Furthermore, thepermeability of the filter fabric layer 16 should be such that static orun-pressurized water in the root zone layer 18 is held up by theperching layer, but upon the turf receiving irrigation water orrainwater, water percolating downwardly through the root zone layer 18will increase the water pressure on the filter fabric layer 16 and thuscause water to flow freely through the filter fabric layer 16 and theintermediate layer 14. A suitable material for use as the filter fabriclayer is a polyester spunbond non-woven fabric having a weight in arange of from about 65 gsm to about 205 gsm, and more preferably in arange of from about 110 gsm to about 150 gsm.

It will be appreciated that the thickness and composition of each of thelayers of the subsurface drainage system 10 may be varied widelydepending on factors, such as climate conditions, availability ofmaterials, and intended use of the turf.

FIGS. 2 and 2A illustrate another subsurface drainage system 10 a whichis similar to the subsurface drainage system 10 described above exceptthat a hydronic piping network 30 is shown disposed in the root zonelayer 18 near the filter fabric layer 16 so that the hydronic pipingnetwork 30 is positioned within the perched water table 24. By havingthe hydronic piping network 30 positioned within the perched water table24, the water will function as a heat exchanger to facilitate heatingand cooling of the root zone layer 18. Hydronic piping networks andtheir components are well known in the art. Thus, no further descriptionof its components, construction, or operation is believed necessary inorder for one skilled in the art to understand and implement thesubsurface drainage system 10 a of the present invention.

FIG. 3 shows another embodiment of a subsurface drainage system 10 bconstructed in accordance with the present invention. The subsurfacedrainage system 10 b is similar to that disclosed above and in U.S. Pat.No. 5,848,856 which is hereby expressly incorporated herein byreference. The subsurface drainage system 10 b includes a base layer 40having at least one sloped surface 41, a drainage collection point (notshown) at the bottom of each sloped surface, and an intermediate layer42 formed by a drain structure overlying the base layer 40, a filterfabric layer 44, a root zone layer 46, and a turf 48.

The drain structure 42 is a thermoplastic mat with a laterally extensivebacking grid having a plurality of struts 43 a defining grid openingstherebetween and a plurality of spaced tubular support members 43 bprojecting from the backing grid 43 a, whereby fluid may flow throughthe backing grid 43 a and between the support members 43 b. The filterfabric layer 44 is a semipermeable geotextile fabric disposed in flushcontact upon the drain structure 42, and preferably, but optionally, animpermeable liner 50 is disposed between the base layer 40 and the drainstructure 42. In instances where it is desirable to allow some permanentdeep infiltration of surface drainage, the impermeable liner 50 may bereplaced with a semi-permeable geotextile fabric.

The subsurface drainage system 10 b further includes a hydronic pipingnetwork 52 disposed in the root zone layer 46 near the filter fabriclayer 44 so that the hydronic piping network 52 is positioned within aperched water table 54. By having the hydronic piping network 52positioned within the perched water table 54, the water will act as aheat exchanger to facilitate heating or cooling of the root zone layer46, as desired. Hydronic piping networks are well known in the art.Thus, no further description of its components, construction, oroperation is believed necessary in order for one skilled in the art tounderstand and implement the subsurface drainage system 10 b of thepresent invention.

FIG. 4 shows a subsurface drainage system 10 c for an artificial turf 68constructed in accordance with the present invention. The subsurfacedrainage system 10c includes a base layer 60 having at least one slopedsurface 61, a drainage collection point (not shown) at the bottom ofeach sloped surface 61, and an intermediate layer 62 formed by a drainstructure overlying the base layer 60, a filter fabric layer 64, anupper layer 66, and the artificial turf 68. The artificial turf 68 isprovided with a porous backing 69 such as a geotextile fabric or fabricwith holes formed therein to permit drainage therethrough.

The drain structure 62 is a thermoplastic mat with a laterally extensivebacking grid having a plurality of struts defining grid openingstherebetween, and a plurality of spaced support members projecting fromthe backing grid, whereby fluid may flow through the backing grid andbetween the support members. An impermeable liner 70 is disposed betweenthe base layer 60 and the drain structure 62. In instances where it isdesirable to allow some permanent deep infiltration of surface drainage,the impermeable liner 70 may be replaced with a semi-permeablegeotextile fabric.

The upper layer 66 may be formed of sand, gravel, rubber, a porous pad,or combinations thereof.

The subsurface drainage system 10 c further includes a hydronic pipingnetwork 72 disposed in the upper layer 66 near the filter fabric layer64 so that the hydronic piping network 72 is positioned within theperched water table 74. By having the hydronic piping network 72positioned within the perched water table 74, the water will act as aheat exchanger to facilitate heating and cooling of the upper layer 66and thus the artificial turf 68. Hydronic piping networks are well knownin the art. Thus, no further description of its components,construction, or operation is believed necessary in order for oneskilled in the art to understand and implement the subsurface drainagesystem 10 c of the present invention.

From the above description, it is clear that the present invention iswell adapted to carry out the objects and to attain the advantagesmentioned herein, as well as those inherent in the invention. While apresently preferred embodiments of the invention have been described forpurposes of this disclosure, it will be understood that numerous changesmay be made which will readily suggest themselves to those skilled inthe art and which are accomplished within the spirit of the inventiondisclosed and as defined in the appended claims.

1. A subsurface drainage system for a playing surface, comprising: asubgrade; an intermediate layer disposed over the subgrade and formedfrom at least one material to define a drainage blanket layer; a layerof semi-permeable filter fabric disposed over the intermediate layer,the layer of filter fabric having a permeability less than thepermeability of the intermediate layer and such that the layer of filterfabric functions as a perching layer to support a perched water tableabove the layer of filter fabric; an upper permeable layer disposed overthe layer of filter fabric and on which the playing surface is disposed;and a hydronic piping network disposed in the upper layer near the layerof filter fabric so that the hydronic piping network is positionedwithin the perched water table such that the water of the perched watertable functions as a heat exchanger to facilitate heating and cooling ofthe upper layer upon the hydronic piping network being heated or cooled.2. The subsurface drainage system of claim 1 wherein the layer of filterfabric is a polyester spunbond non-woven fabric having a weight in arange of from about 110 gsm to about 150 gsm.
 3. The subsurface drainagesystem of claim 1 wherein the subgrade is contoured to define one ormore surfaces sloping down to points or lines of fluid collection. 4.The subsurface drainage system of claim 1 wherein the intermediate layeris formed at least one material selected from the group consisting ofcrushed stone, pea gravel, rubber particles, and combinations thereof.5. The subsurface drainage system of claim 1 wherein the intermediatelayer is a thermoplastic mat having a laterally extensive backing gridand a plurality of spaced tubular support members projecting from thebacking grid whereby fluid may flow through the backing grid and thesupport members.
 6. The subsurface drainage system of claim 1 whereinthe upper layer is a root zone layer comprising at least one materialselected from the group consisting of sand, organic matter, inorganicmatter and combinations thereof.
 7. A subsurface drainage system forregulating the temperature of a root zone, comprising: a semi-permeablefilter fabric having a permeability such that the filter fabricfunctions as a perching layer to support a perched water table above thefilter fabric; a root zone layer disposed over the layer of filterfabric; a natural turf layer disposed on the root zone layer; and ahydronic piping network disposed in the root zone layer near the layerof filter fabric with the hydronic piping network positioned within theperched water table such that the water of the perched water tablefunctions as a heat exchanger to facilitate heating and cooling of theroot zone layer upon the hydronic piping network being heated or cooled.8. The subsurface drainage system of claim 7 wherein the layer of filterfabric is a polyester spunbond non-woven fabric having a weight in arange of from about 110 gsm to about 150 gsm.
 9. A subsurface drainagesystem for regulating the temperature of an artificial turf, comprising:a semi-permeable filter fabric having a permeability such that thefilter fabric functions as a perching layer to support a perched watertable above the filter fabric; a permeable upper layer disposed over thelayer of filter fabric; an artificial turf layer disposed on the upperpermeable layer; and a hydronic piping network disposed in the upperpermeable layer near the layer of filter fabric with the hydronic pipingnetwork positioned within the perched water table such that the water ofthe perched water table functions as a heat exchanger to facilitateheating and cooling of the upper permeable layer and thus the artificialturf layer upon the hydronic piping network being heated or cooled. 10.The subsurface drainage system of claim 9 wherein the layer of filterfabric is a polyester spunbond non-woven fabric having a weight in arange of from about 110 gsm to about 150 gsm.